Cycloolefins can be polymerized through the olefin structure to yield polycycloaliphatics, or through a ring-opening process to yield unsaturated linear polymers. The latter process has particular appeal since the resulting polymers are sulfur-vulcanizable. Cyclopentene is a readily available ethylene production by-product, and considerable art has focused on the ring-opening polymerization and copolymerization of cyclopentene. Dicyclopentadiene is another readily available ethylene production by-product, but not as much consideration has been given in the prior art to dicyclopentadiene polymers. Recent U.S. Patents directed to cyclopentene and dicyclopentadiene polymers include U.S. Pat. Nos. 3,778,420, 3,781,257, 3,790,545, 3,853,830, and 4,002,815.
Norbornene (bicyclo[2.2.1]-hept-2-ene) and substituted norbornenes can be produced by Diels-Alder reaction of cyclopentadiene with selected olefins. U.S. Pat. No. 3,074,918 is directed to polymerization of cyclic olefins having at least one unsubstituted ring double bond and not more than one double bond in each ring, such as dicyclopentadiene, 1,2-dihydrodicyclopentadiene, norbornene, or substituted norbornenes. Other U.S. patents directed to norbornene and substituted norbornene polymers include U.S. Pat. Nos. 2,721,189, 2,831,037, 2,932,630, 3,330,815, 3,367,924, 3,467,633, 3,546,183, 3,836,593, 3,879,343, and 4,020,021.
Polymers of dicyclopentadiene alone or with acyclic monoolefins or nonconjugated acyclic olefins are difficult to process. Moreover, such polymers suffer from oxidative instability because of the presence of unsaturation in the dicyclopentadiene ring pendant from the polymer backbone. 1,2-Dihydrodicyclopentadiene polymers overcome the oxidative instability disadvantage (since the pendant ring contains no unsaturation), but processing difficulties remain.
New copolymers are desired having both improved oxidative stability and processability.